Method and system for controlling a laser-based lighting system

ABSTRACT

The present invention concerns a method for controlling a laser-based lighting system comprising a scanning mirror arrangement, arranged to be rotatable around two substantially orthogonal axes. The method comprises: (a) a sensor capturing a first image; (b) the sensor sending data representing at least part of the first image to an image generation unit; (c) the image generation unit generating a second image based on the data representing at least part of the first image, wherein the generated second image comprises information representing a feature region in the first image; (d) the image generation unit sending the second image to a projection system controller; and (e) the projection system controller, based on the received second image, controlling the operation of a projection system comprising a laser light source; and a scanning mirror arrangement for receiving the light radiated by the laser light source, and for reflecting the received light to a wavelength conversion element to project the second image. In the method the second image is streamed to the projection controller as an image pixel stream without first saving it in a memory.

TECHNICAL FIELD

The invention relates to the field of lighting systems to be used forinstance in automotive headlights or camera flashes. More specifically,the present invention relates to laser-based illumination systemscomprising at least one scanning mirror arrangement. The invention alsorelates to a corresponding illumination method and to a computer programproduct.

BACKGROUND OF THE INVENTION

Scanning mirror based light projection systems are known in the field ofillumination systems. WO2013/029667 and US2014/0029282 disclose examplesof such systems, where the light source is a laser type light source.The advantage of using a laser light source is or example thatlaser-based illumination systems can generate very pure white light. Ascanning mirror rotatable around two orthogonal axes is actuated andreceives a light signal from a primary light source to project an imageon to a phosphorous element. The light radiated by the primary lightsource, or more specifically its luminous intensity, for example, can bemodulated to project a desired image on to the phosphorous element. Thephosphorous element is then arranged to perform a wavelength conversionof the light signal received from the primary light source. Consequentlythe phosphorous element, acting as a secondary light source, re-emitslight, which when combined with the light from the primary light sourceproduce useful white light in different directions. In this kind ofsystem a very high overall energy efficiency can be obtained as thewavelength conversion done by the phosphorous element is more energyefficient than the electrical-to-optical conversion done by the laserlight source. Instead of using one scanning mirror rotatable around twoorthogonal axes, it possible to use two mirrors instead, each movablearound one axis, where the two axes are mutually orthogonal. This kindof lighting system can be used for example in vehicle headlights.

It is, however, difficult to efficiently control the above describedillumination system to truly provide a smart illumination system, whichcould for instance, when applied to vehicle headlights, adapt theillumination to take into account current road conditions. For instance,the solution disclosed in US2014/0029282 does not provide sufficientcontrol of the illumination system to be considered a truly smartillumination system. For instance, the illumination beam is not capableof moving horizontally or vertically. Furthermore, generally inheadlights, three different light bulbs are needed: one for low beam,one for full beam and one for the indicator. Typically, each of theselight bulbs is controlled by its own motor. However, this is not anoptimal solution in terms of use of space and energy consumption.Moreover, the currently available image projection systems need at leastone image frame or line buffer to temporarily store the images andpossibly modify it before it is projected. Such a buffer is needed inthe current solutions at least in the graphics processing unit (GPU)connected to a projector, but often also the projector comprises asimilar buffer. Reading data from the buffer consumes energy and alsomeans that the projected image cannot be modified in real-time.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome the problemsidentified above related to the laser based illumination solutions.

According to a first aspect of the invention, there is provided a methodof controlling a laser-based lighting system comprising a scanningmirror arrangement, arranged to be rotatable around two substantiallyorthogonal axes, the method comprising:

-   -   a sensor capturing a first image;    -   the sensor sending data representing at least part of the first        image to an image generation unit;    -   the image generation unit generating a second image based on the        data, wherein the generated second image comprises information        representing at least one feature region in the first image;    -   the image generation unit sending the second image to a        projection system controller; and    -   the projection system controller, based on the received second        image, controlling the operation of a projection system        comprising a laser light source; and the scanning mirror        arrangement for receiving the light radiated by the laser light        source, and for reflecting the received light to a wavelength        conversion element to project the second image,

wherein sending the second image to the projection system controllercomprises streaming the second image to the projection controller as animage pixel stream.

The proposed solution provides a smart illumination method according towhich there is no need to save the projected image in a memory before itis projected. Thus, any modifications in the image to be projected maybe carried out substantially in real time. Furthermore, the projectionsystem can start projecting the image even before the whole image pixelstream has been received by the projection system controller. Theproposed solution also offers a seamless cooperation of the elementsinvolved in the method allowing the image captured by the sensor toaffect the actual projected image.

According to a variant of the first aspect, the method comprisesproviding a default projection image, and masking the default projectionimage using the information representing the feature region in the firstimage.

According to another variant of the first aspect, the operation of thelaser light source is controlled by adjusting the pixel brightness ofthe pixels of the image currently being projected to match the pixelbrightness of the second image.

According to another variant of the first aspect, the pixels outside thefeature region have a higher brightness value than the pixels inside theshape.

According to another variant of the first aspect, all the pixels outsidethe feature region have the same brightness value.

According to another variant of the first aspect, at least some of thepixels inside the feature region have different brightness values fromeach other.

According to another variant of the first aspect, the pixel brightnessis adjusted by adjusting the input current of the laser light source.

According to another variant of the first aspect, controlling theoperation of the projection system comprises applying an offset signalto an actuation signal of the scanning mirror arrangement.

According to another variant of the first aspect, controlling theoperation of a projection system comprises adjusting the amplitude ofoscillations of at least one mirror of the scanning mirror arrangement.

According to another variant of the first aspect, sending datarepresenting at least part of the first image comprises streaming thedata to the image generation unit.

According to another variant of the first aspect, the sensor defines thefeature region before sending the data comprising informationrepresenting the feature region to the image generation unit.

According to another variant of the first aspect, information definingthe location of the feature region within the first image is sent to theimage generation unit.

According to another variant of the first aspect, all the pixelsdefining the first image are sent and where the feature region isdefined by certain pixel values.

According to another variant of the first aspect, one light pulse fromthe laser light source represents one image colour.

According to another variant of the first aspect, the informationrepresenting the feature region comprises one or more mathematicalequations.

According to another variant of the first aspect, the projection systemcontroller when controlling the operation of the projection system takesinto account parameter values detected by a parameter detector.

According to another variant of the first aspect, the parameter valuescomprise at least one of the following: speed of movement of thelighting system; angle of turning of the lighting system; inclination ofthe lighting system; and ambient level of light.

According to another variant of the first aspect, the second image isstreamed without first saving it in an intermediate storage.

According to a second aspect of the invention, there is provided acomputer program product comprising instructions for implementing thesteps of the method according to the first aspect when loaded and run oncomputer means of a laser-based lighting system.

According to a third aspect of the invention, there is provided a laserbased lighting system comprising:

-   -   a sensor for capturing a first image and for sending data        representing at least part of the first image to an image        generation unit;    -   the image generation unit for generating a second image based on        the data, wherein the generated second image comprises        information representing at least one feature region in the        first image; and for sending the second image to a projection        system controller;    -   the projection system controller for controlling, based on the        received second image, the operation of a projection system;    -   the projection system for projecting the second image, the        projection system comprising a laser light source; and a        scanning mirror arrangement for receiving the light radiated by        the laser light source, and for reflecting the received light to        a wavelength conversion element; and    -   the wavelength conversion element for projecting the second        image,

wherein the image generation unit is arranged to stream the second imageto the projection controller as an image pixel stream.

Other aspects of the invention are recited in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will become apparent fromthe following description of a non-limiting exemplary embodiment, withreference to the appended drawings, in which:

FIG. 1 is a simplified block diagram showing an exemplary lightingarrangement according to one aspect of the present invention;

FIG. 2 illustrates schematically how to project an image on to awavelength conversion element according to one example;

FIG. 3 illustrates schematically how to move a projected imagevertically on a wavelength conversion element; and

FIG. 4 is a flow diagram illustrating an exemplary method of controllingthe operation of a lighting system.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

An embodiment of the present invention will now be described in detailwith reference to the attached figures. Identical or correspondingfunctional and structural elements which appear in the differentdrawings are assigned the same reference numerals. The teachings of theinvention are explained in detail in the context of an automotiveapplication, but the invention is by no means limited to thisenvironment.

FIG. 1 is a schematic block diagram illustrating an exemplary lightingsystem according to an embodiment of the present invention. Thisarrangement may be used for example in the headlights of a vehicle, suchas a car, or in photographic flash applications. In FIG. 1 there isshown a projection system 1, or simply a projector, which in thisexample is a MEMS (Micro-Electro-Mechanical System) scanningmirror-based projection system. This projection system 1 comprises ascanning system 3, which in this example has one mirror arranged to berotated around two orthogonal axes. However, the scanning system couldalternatively have two mirrors, each arranged to be tilted around one ofthe two orthogonal axes. The scanning mirror may be actuated usingmagnetic, electrostatic, thermal, piezo-electric, hydraulic, pneumatic,chemical or acoustic means. This kind of optical scanning system issometimes called a “scanner”. The advantage of a scanning system is thata real image can be projected on to a wavelength conversion element 5,allowing the brightness of the image to be locally controlled so that,as explained later, the resulting projected and reflected light beam canhave local brightness adjustments to avoid temporarily dazzling orblinding drivers of oncoming vehicles when the lighting system is usedin a vehicle headlight.

The projection system 1 also includes a light source 7, and morespecifically a laser light source which is arranged to emit light at onewavelength. In this particular example the light emitted is anultraviolet (UV) or near-UV light having wavelength of 360 nm to 480 nm.However, other types of laser could be used, from UV light to visiblelight and infra-red light. The light source 7 is arranged to emit lighton to the scanning system 3. The laser beam generated by the lightsource is thus deviated in two orthogonal planes by the scanning systemand it emerges in a solid angle projecting on to all or part of thesurface of the wavelength conversion element 5, such as, for example, aphosphor plate or a plate on which preferably a continuous andhomogeneous layer of phosphor has been deposited. Each point on thephosphor plate of the wavelength conversion element 5 receiving thelaser beam A from the scanning system, typically monochromatic andcoherent, absorbs the laser power and then re-emits a light B of adifferent wavelength. The resulting combined light can be considered as“white”, since it contains a plurality of wavelengths between about 400nm and 800 nm, i.e. in the visible light spectrum. It is to be notedthat the projection system can also be used in night-visionapplications. The scanning system 3 is arranged to deflect the laserlight following various kinds of pattern, such as a Lissajous pattern ora raster pattern (interlaced or non-interlaced). FIG. 2 illustrates atypical raster pattern projection, where the light is deflected so thatlines are scanned from left to right and then from right to left, fromtop to bottom or vice-versa. Within the raster pattern projection, theimage can also be displayed during the so-called fly-back scanningpattern (in a typical raster scan display, the MEMS mirror displays theimage only in one sweep of the mirror controlling the refresh rate,however in the fly-back option, the same or another pattern may bedisplayed on the other sweep of the mirror) or other patterns could beused, where the direction of the pattern can be switched (verticalscanning instead of horizontal scanning, therefore where the image isscanned to display vertical lines and to display all the lines from leftto right or vice-versa), or where the screen is scanned using any kindof space filling curve, for example Peano, Hilbert, or other fractal orL-system curves.

A reflector element 9 may be placed behind the wavelength conversionelement 5 and may have substantially the same surface area as thewavelength conversion element 5. The reflector element may be a platewhich is substantially parallel to the wavelength conversion element 5.The distance between the wavelength conversion element 5 and thereflector element 9 may be between 0 cm to 15 cm for example. In otherwords, the wavelength conversion element may be in direct contact withthe reflector element 5. The size of the reflector element may bebetween 0.1 cm×0.1 cm and 20 cm×20 cm for example. The size may be forexample from 0.1 cm×0.1 cm to 5 cm×5 cm for photographic flashapplications and from 1 cm×1 cm to 20 cm×20 cm for headlampapplications. The reflector element is arranged to reflect light emittedmainly by the wavelength conversion element 5 in a desired direction. Bylocating the reflector at the rear side of the wavelength conversionelement 5 no light, or only very little light, reaches a rear part of ahousing, opposite to where the projection system 1 is located as shownin FIG. 1. Alternatively, instead of using a flat mirror reflector, thereflector may be curved so that the reflected light is shaped by thisreflector. For example, if the mirror has a concave curvature, thereflected light will be more concentrated, in other words the maximumdistance between all the reflected beams B will be smaller than with aflat reflector. Alternatively, the reflector can also be a prismatictape such as DOT C tapes or has a tetrahedral or octahedral structure tomake it retro-reflective. It is also possible to use a reflective arraycomprising micro-focal elements as the reflector. The micro-focalelements may be microlenses or micro-mirrors, also referred to asmicro-reflectors, whose largest dimension (e.g. diameter) may be in therange 1 μm to 5000 μm, for example, or more particularly in the range 50μm to 1000 μm. Thus, if each of the lenses in the array is touching itsneighbours, the array pitch is also in the range 1 μm to 5000 μm, forexample, or more particularly in the range 50 μm to 1000 μm. Thereflecting angle, also called a diffusing angle, of these microfocalelements is from a few degrees up to 180 degrees. It is to be noted thatone array may comprise a mixture of different micro-focal elements, forinstance a mixture of micro-focal elements of different sizes, shapesand/or focal lengths. In other words, the micro-focal elements in onearray do not have to be of the same type.

The reflector element 9 in the illustrated example has an array ofspecifically shaped optical elements, so that the reflected light beamcan be shaped more accurately than without these optical elements, andthe use of the reflected or re-emitted light can be made more efficient,as it will be radiated directly in the right direction and with thedesired beam profile. The reflector element 9 thus provides a beamshaping capability. For example, the reflected light from the reflectorelement 9 may be shaped to exit the headlight directly without firstbeing reflected from the surface of the housing. Indeed, any internalreflection from the surface of the housing incurs a light loss becausethat surface typically only has a reflectivity of 85%, and thusrepresents a light loss of 15%. It is also to be noted that, thanks tothe lens array, there is no need for any supplementary optical imagingsystems in the lighting arrangement to direct the light beams in adesired direction.

The lighting arrangement in FIG. 1 further comprises a sensor unit 11which in this example is a camera or an ambient light sensor. In case ofan ambient light sensor, the sensor unit 11 can be arranged to detectcurrent light conditions of the lighting arrangement. In case of acamera, the sensor unit 11 is arranged to detect objects and/or currentenvironmental conditions of the lighting arrangement. For instance, whenapplied to a vehicle, the camera is arranged to detect the current roador driving conditions. For example, it may detect oncoming vehicles. Itmay also detect road signs, markings, traffic lights etc. In thisexample the camera is connected to an image/video generation unit 13,also called a GPU, which is arranged to generate an image of whichpurpose will be explained later. This image, or more specifically asignal representing this image, is in this example arranged to be sentto a projector system controller 15 via a communication link. In thefigure there is also shown a parameter detector 17, which in thisexample is a driving parameter detector 17, which is arranged to detectat least some current driving related parameters. For example, it maydetect whether the vehicle is turning and if so in which direction, orwhether the vehicle is going downhill or uphill. Thus, the drivingparameter detector may have a sensor connected to it, or the sensor maybe part of the driving parameter detector 17. In this example, thedriving parameter detector 17 is connected to the GPU 13. There may beone or more of each of the elements 11, 13, 15 and 17 per vehicle.

The projector system controller 15 is arranged to control, i.e.determine the behaviour of the operation of the projection system 1.More specifically, it is configured to control the operation of thelaser light source 7 and the scanning system 3. The laser light source 7can be controlled by adjusting the current that flows to laser diodes.In this way the brightness of the light beam emitted by the laser sourcecan be adjusted. The brightness may also be referred to as a luminousintensity, in other words it is the perceived light power per unit solidangle. Thus, by varying the laser light output modulation, a part of theimage can be illuminated on the wavelength conversion element 5, whileanother part may not be illuminated.

The entire projected image can be offset by applying an offset signal ontop of an actuation signal of the scanning system. If this offset signalis applied to the mirror that generates the vertical component of theprojected image, then the image can be shifted vertically as illustratedin FIG. 3, where the dashed lines represent the old image and the solidlines represent the currently projected image. If, on the other hand,the offset signal is applied to the mirror that generates the horizontalcomponent of the image, then the image can be shifted horizontally. Inthis manner, for instance, it is possible to avoid dazzling ortemporarily blinding the drivers of oncoming vehicles. The actuationsignal may be at a different frequency than the fundamental resonancefrequency of the mirror. In this manner the mirror or mirrors move(s)according to a linear motion instead of a sinusoidal motion. This isthen providing a so-called “static” movement of the mirror.

By adjusting the amplitude of oscillations of the scanning mirror, it ispossible to vary the size of the projected image. This is achieved byadjusting the amplitude of the actuation signal of the scanning system3. For instance, reducing the amplitude of oscillation of the mirrorgenerating the horizontal component of the image will reduce thehorizontal distance on the wavelength conversion element 5 over whichthe light is scanned. Reducing the amplitude of oscillations of themirror generating the vertical component of the image will reduce thevertical distance on the wavelength conversion element 5 over which thelight is scanned. Thus, the whole of the image is now projected over asmaller portion of the display area 2 than without this adjustment.Thus, the whole image 3 will appear smaller than its original size. In acorresponding manner, the image size can be increased by increasing theamplitude of the oscillations. This technique may be used to increase ordecrease the brightness of the resulting light beam as the light will bemore or less concentrated.

Thus, by controlling the operation of the projector system 1 by theprojector system controller 15 based on the information received fromthe driving parameter detector 17 and/or from the sensor 11, anillumination pattern which changes based on the environmental conditionsand/or driving parameters is obtained in front of the vehicle. If theoperation of the scanning system 3 is controlled and if it iselectrostatically, piezo-electrically or thermally actuated, then thecontrolling may be carried out by varying the voltage applied to thescanning system. However, if the scanning system 3 is actuatedmagnetically, then controlling may be carried out by varying the currentor voltage applied to the scanning system. It is to be noted that thecontrol methods described above can be combined so that the effects takeplace simultaneously.

An illumination method according to an example of the present inventionis now explained more in detail with reference to the flow chart of FIG.4. In step 21 the sensor detects an object or captures a first image.This object may be for instance a windshield of an oncoming vehicle, arear windshield of a vehicle in front, or in photography applicationsthe object may be the head of a person to be photographed. For instance,detecting a windshield from a car chassis is quite easy due to thedifference in the light reflection (for example illuminated by theheadlamps). Thus, little computing power is required, and the shape ofthe windshield is also a simple trapezoidal shape, which can be definedby a simple equation. Another example of a simple equation is a circledefined mathematically with the following equation: (x−a)²+(y−b)²=r²,where a and b define the position of the circle centre along x and yaxes, respectively, and r is the radius of the circle. This circle mayadvantageously cover the detected object, which may be a vehicle or partof it or a person's head. The shape, also referred to as feature region,defined in this manner may not be illuminated or the pixel values insidethe shape should at least have a low brightness value. One way to definethe radius is to get the distance from the object from the sensor 11and/or the driving parameter detector 17. It is to be noted that thesensor 11 may also determine the distance to the object bytriangulation. For a random shape, the equation may be a set ofequations or line segments, in which case the area enclosed in by thesegments defines the resulting shape.

Based on the detected object or the captured image (first image), instep 23 the sensor 11 defines a shape or pattern such as a polygonalshape, whose size and shape correspond to the size and shape of thedetected object (e.g. car windshield). The size of the shape may bescaled with respect to the size of the detected object by using a givenconversion table, for example to take into account the distance to theobject. This shape will be visible in the image (second image) whichwill be projected on to the wavelength conversion element 5 as explainedlater in more detail. In step 25 some data representing the shape issent to the GPU. In this example, the data is streamed as a data stream.According to a first option, the sensor 11 provides only the data streamrelated to the location of the shape within the image to be projected.For example, the following information may be streamed to the GPU 13:line 0, pixels 0 to 25; line 1, pixels 2 to 20 etc. Here the linenumbers refer to the order of the pixel line numbers in the image to beprojected. According to a second option, the sensor 11 provides acomplete first image pixel stream to the GPU 13. According to thisoption, also the pixel values are provided, or more specifically thepixel brightness values. If a value deviates from a predetermined value,then it can be determined that these pixels are outside the shape. Inthis way the GPU 13 can determine the exact location of the shape in theimage to be projected. For instance, the following pixel stream may besent to the GPU 13: line 0, pixel 0, pixel value=0; line 0, pixel 1,pixel value=0; line 0, pixel 2, pixel value=0; line 0, pixel 3, pixelvalue=1; line 0, pixel 4, pixel value=1; . . . ; line 10, pixel 4, pixelvalue=255 etc. In this example the pixel value 255 is the maximum valueand thus it can be determined that this pixel is outside the shape,whereas pixels having a pixel value different from this value are partof the shape. Above a raster image was assumed, but vector or otherimages may also be used with suitable amendments. Indeed, the pixelsoutside the shape all have the same pixel value, which may be the valuerepresenting the maximum pixel brightness. The pixels which are insidethe shape may have different pixel values from each other. It is alsopossible that the sensor 11 sends a data stream of the first image tothe GPU 13 without defining any shapes in the stream. In this case theGPU 13 would extract one or more shapes from that stream and combinethose shapes with a default image (third image). Typically the first,second and third images are all different from each other and, asexplained below, the second image is obtained from the first and thirdimages by combination.

Once the GPU 13 has received the data stream from the sensor 11, thenthis data stream is combined with the pixels of the default image. Thismay be done by masking the default projection image using theinformation representing the shape in the first image. This may be doneby deducting pixel by pixel the data stream from the pixels of thedefault image, which is generally larger than the first image in termsof number of pixels. In other words, the pixels corresponding to theshape in the data stream replace the corresponding pixels in the defaultimage. The default image may for instance be a white image with all thepixels having a maximum brightness. In addition to that, if the firstoption above is used, then the GPU 13 defines the pixel values insidethe shape. By default, the pixel values inside the shape may havebrightness values set to zero. Alternatively, the pixel values may bedefined based on further information received from the sensor 11 and/orbased on information received from the driving parameter detector 17. Itis to be noted that it is possible that the first image size isdifferent from the third image size. If the second option above is used,then at least the pixel values inside the shape have already beendefined.

In step 29 the GPU 13 may receive some driving related parameters, suchas the position of the driving wheel, speed of travel of the vehicle,inclination of the vehicle etc from the driving parameter detector 17.Some of these parameters may be obtained by a satellite positioningsystem connected to the driving parameter detector 17. It is alsopossible that a button or other control input is operated manually by adriver for example to send a signal to the driving parameter detector 17to adjust the height of the headlights. In step 31 the GPU converts thereceived driving related parameters to a command to change the defaultimage size and/or to move it horizontally and/or vertically. Of course,this conversion could be done by the projector system controller 15instead. In step 33 the GPU streams the image pixel stream to theprojector system controller unit 15 if necessary together with themanual command mentioned above, or the command may be sent to theprojector system controller 15 separately. In this manner, there is noneed to have an image buffer in the GPU 13 or in the projector systemcontroller 15 for caching or saving the second image. By not having tostore and/or read the image from a memory has, the present imagingmethod can operate faster than previous solutions and, according to thisinvention, the image pixels can be modified and projected substantiallyin real time. Accordingly, by sending a signal to directly control thecurrent applied to the mirror system and/or to the laser diodes of thelight source 7, the response time to any desired modifications in theimage can be optimised. The image pixel stream speed may be adaptedbased on the speed of the vehicle (obtained from the driving parameterdetector 17), so as to send the pixel information to the projectorsystem controller 15 at the right speed, so that the resulting generatedsecond image to be projected takes the speed of the vehicle intoaccount.

In step 35 the projector system controller 15 transforms digitalinformation, i.e. the second image pixel stream and/or the command, fromthe GPU into current and/or voltage output which is sent to the scanningsystem 3 and/or to the laser diodes. In this manner the operation of theprojection system 1 can be controlled substantially in real time, andthe projected image takes into account, substantially in real time, anychanges detected by the sensor 11.

According to the teachings above, various kinds of images which takeinto account the varying external conditions may be projected on to thewavelength conversion element 5 to be further reflected towards thefront of the imaging system. The projected image may take various forms.For example an arrow may be displayed on a road to show a driver thedirection where to go. This arrow may be displayed by projecting lightall-around the arrow but leaving the arrow itself darker, i.e. lessbrightly illuminated. In this manner the driver obtains drivinginformation, but can still see the road, because it remains illuminated.According to another example, the projected image could illuminate theroad, but leave a dark or black line or region on one or both sides ofthe white line or marking on the road to increase the contrast betweenthe road and the line or marking as perceived by the human eye. In thiscase the dark or black line may be essentially contiguous with the whiteline or marking on the road. According to a further example, theteachings above may be used in switching between left-hand andright-hand-drive cars. In the past, all manufacturers had to produce twodifferent types of headlamp units for left-hand-drive andright-hand-drive countries. For example, in some left-hand-drivecountries the authorities require right-hand-drive cars to be fittedwith a beam-bender as a temporary measure (e.g. for tourists' cars), orchanging the headlamps completely if the car is to be imported. Abeam-bender is a kind of plastic Fresnel lens glued to the glass of theheadlamp. With the present invention the changes can be simply done bychanging the car's user preferences in software. According to a furtherexample, the projector may be used in photographic flashes to illuminatethe darker areas and then to correct accordingly the sensor returnedvalues so as to provide a high dynamic range capture of the camera imagesensor.

The above described embodiment can be varied in multiple ways. Forinstance, a power-safe mode can be used in the system so that if thesensor 11 and/or the driving parameter detector 17 do not detect anychanges, no computing is done by the GPU 13 and the pixel output streamto the projector system controller 15 remains constant. If the teachingsabove are applied to photographic flash applications, the parameterdetector may be an ambient light sensor. The information from thissensor may be used to adjust the pixel brightness values of the image tobe projected. In this manner illumination of certain parts of the imageor the whole image can be adjusted.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, such illustration and descriptionare to be considered illustrative or exemplary and not restrictive, theinvention being not limited to the disclosed embodiment. Otherembodiments and variants are understood, and can be achieved by thoseskilled in the art when carrying out the claimed invention, based on astudy of the drawings, the disclosure and the appended claims.

In the claims, the word “comprising” does not exclude other elements orsteps, and the indefinite article “a” or “an” does not exclude aplurality. The mere fact that different features are recited in mutuallydifferent dependent claims does not indicate that a combination of thesefeatures cannot be advantageously used.

The invention claimed is:
 1. A method, comprising: capturing a firstimage; sending data representing at least part of the first image to animage generation unit; generating, at the image generation unit, asecond image based on the data, wherein the generated second imagecomprises information representing at least one feature region in thefirst image; streaming the second image to a controller for a projectionsystem as an image pixel stream, the projection system comprising alaser light source, a scanning mirror apparatus, and a wavelengthconversion element, the scanning mirror apparatus arranged to receivelight radiated by the laser light source and rotate around twosubstantially orthogonal axes to reflect the received light to thewavelength conversion element to project the second image; andprojecting the second image via the projection system.
 2. A methodaccording to claim 1, comprising providing a default projection image,and masking the default projection image using the informationrepresenting the feature region in the first image.
 3. A methodaccording to claim 1, comprising adjusting the pixel brightness of thepixels of the image currently being projected to match the pixelbrightness of the second image.
 4. A method according to claim 3,wherein the pixels outside the feature region have a higher brightnessvalue than the pixels inside the shape.
 5. A method according to claim3, wherein all the pixels outside the feature region have the samebrightness value.
 6. A method according to claim 3, wherein at leastsome of the pixels inside the feature region have different brightnessvalues from each other.
 7. A method according to claim 3, comprisingadjusting the input current of the laser light source.
 8. A methodaccording to claim 1, comprising applying an offset signal to anactuation signal of the scanning mirror apparatus.
 9. A method accordingto claim 1, comprising adjusting the amplitude of oscillations of atleast one mirror of the scanning mirror apparatus.
 10. A methodaccording to claim 1, wherein sending data representing at least part ofthe first image comprises streaming the data to the image generationunit.
 11. A method according to claim 1, comprising defining the featureregion before sending the data comprising information representing thefeature region to the image generation unit.
 12. A method according toclaim 11, wherein information defining the location of the featureregion within the first image is sent to the image generation unit. 13.A method according to claim 11, wherein all the pixels defining thefirst image are sent and where the feature region is defined by certainpixel values.
 14. A method according to claim 1, wherein one light pulsefrom the laser light source represents one image color.
 15. A methodaccording to claim 1, wherein the information representing the featureregion comprises one or more mathematical equations.
 16. A methodaccording to claim 1, wherein the projection system controller whencontrolling the operation of the projection system takes into accountparameter values detected by a parameter detector.
 17. A methodaccording to claim 16, wherein the parameter values comprise at leastone of the following: speed of movement of the lighting system; angle ofturning of the lighting system; inclination of the lighting system; andambient level of light.
 18. A method according to claim 1, wherein thesecond image is streamed without first saving it in an intermediatestorage.
 19. A computer program product, comprising a non-transitorycomputer-readable medium having instructions stored thereon, theinstructions, when executed by a controller for a laser based lightingsystem, implement the method of claim
 1. 20. A laser based lightingsystem comprising: a sensor for capturing a first image and for sendingdata representing at least part of the first image to an imagegeneration unit; the image generation unit for generating a second imagebased on the data, wherein the generated second image comprisesinformation representing at least one feature region in the first image;and for sending the second image to a projection system controller; theprojection system controller for controlling, based on the receivedsecond image, the operation of a projection system; the projectionsystem for projecting the second image, the projection system comprisinga laser light source; and a scanning mirror arrangement for receivingthe light radiated by the laser light source, and for reflecting thereceived light to a wavelength conversion element; and the wavelengthconversion element for projecting the second image, wherein the imagegeneration unit is arranged to stream the second image to the projectioncontroller as an image pixel stream.